JPS61100236A - Correlation detection type ultrasonic blood stream meter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a correlation detection type ultrasonic blood flow meter in which the sample volume is substantially elongated in the ultrasonic beam direction by using a range gate circuit. It is.

[Prior art and problems]

Figure 3 shows a conventional ultrasonic pulse current meter (Japanese Patent Application Laid-Open No. 58-71
11 is a control circuit, 12 is an ultrasonic drive circuit, 13 is a transducer, 14 is a switch, 15 is an amplifier, 16 and 17 are delay circuits, and 18 and 19 are adders. 20 and 21 are receiving amplifiers, 22 is a first amplitude value sample/hold circuit, 23 is a second amplitude value sample/hold circuit, 24 is a cross-correlation peak time difference detection circuit, 25 is a speed calculation circuit, 31 is an ultrasonic wave A pulse Doppler current meter, 32 indicates a vector calculation circuit, respectively.

The ultrasonic drive circuit 12 drives the transducer 13 via the switch 14 in response to a start signal sent from the control circuit 11, and transmits ultrasonic pulses or burst waves to the outside. The reflected waves returning from the outside are
The signal is received by the transducer 13, supplied to the amplifier 15 via the switch 14, and amplified. The output amplified by the amplifier 15 is applied to a set of multiple delay circuits 16 and 17, and based on the same principle as a phase array antenna, the delay time of the delay circuits constituting each set of delay circuits is set to a predetermined time. By setting this, the received ultrasonic waves can be given directivity. Therefore, the set of delay circuits 16 and 1
The 7 sets each take out reflected waves having different directivity, and each set is added to an adder 18 or 19. The output of adder 18 is applied to receive amplifier 20 and amplified;
The first amplitude value sample and hold circuit 22 is supplied as an amplitude sample circuit. The first amplitude value sample and hold circuit 22 samples and holds amplitude data at sample points at the same time, that is, at the same distance, in response to a sample position instruction from the control circuit 11. The reflected wave output having another directivity applied to the adder 19 is applied to the receiving amplifier 21, amplified, and supplied to the second amplitude value sample/hold circuit 23. The second amplitude value sample and hold circuit 23 samples and holds amplitude data at sample points at the same time, that is, at the same distance, in response to a sample position instruction from the control circuit 11. The two data strings generated by the amplitude value sampling and holding described above are applied to the cross-correlation peak time difference detection circuit 24, and the time difference at which the cross-correlation of the two data strings reaches its peak is determined. The output of the cross-correlation peak time difference detection circuit 24 is applied to the speed calculation circuit 25, which is
Divide by the sample-hold interval and the pulse transmission interval to calculate the flow velocity in the direction perpendicular to the beam direction. Note that the sample-hold interval is determined by the angles of the two directivity directions and the distance from the transducer to each sample point. The ultrasonic pulse Doppler current meter 31 measures the flow velocity in the ultrasonic beam direction. The flow velocity output from the velocity calculation circuit 25 and the flow velocity output from the ultrasonic pulse Doppler current meter 31 are input to the vector calculation circuit 32 and added vectorially.

Figure 4 shows the ultrasonic pulse current meter shown in Figure 3.
! The first amplitude value sample and hold circuit 22 and the second amplitude value sample and hold circuit 23 are simply sample and hold circuits.
FIG. 3 is a diagram illustrating a problem when using a hold circuit. In FIG. 4, TD is a transducer row, B1
and B2 indicate the ultrasound beam, and Svl and SV2 indicate the sample volume, respectively. Further, arrows indicate the flow of blood cells.

, as shown in Fig. 4, when the flow of blood cells is not perpendicular to the direction of the ultrasound beam, the sample volumes Sv1 and SV
The number of blood cells passing through both sample volumes decreases, and the correlation between the signals obtained from both sample volumes decreases, making it impossible to accurately detect blood flow velocity.

[Purpose of the invention]

The present invention is based on the above considerations, and aims to provide a correlation detection type ultrasonic blood flow meter that can always accurately measure blood flow velocity without being affected by the direction of blood cell flow. The purpose is

[Means to achieve the purpose]

Therefore, the correlation detection type ultrasonic blood flow meter of the present invention,
A quadrature detector that detects reflected ultrasound signals using sine wave and cosine wave reference waves, respectively, and two ranges that receive orthogonal detection outputs on the sine wave side and cosine wave side of the quadrature detector, respectively.・A gate circuit, a high-pass filter connected to the output sides of the two range gate circuits, a circuit for calculating the sum of squares of the output signals of the two high-pass filters, and a circuit for calculating the sum of squares of the output signals of the two high-pass filters, and a circuit for calculating the sum of squares of the output signals of the two high-pass filters, and The present invention is characterized by comprising a circuit for calculating correlation.

[Embodiments of the invention]

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram showing an example of an amplitude value sample and hold circuit according to the present invention. In Fig. 1, 41A and 41B are multipliers, 42A and 42B are low-pass filters, and 43A and 43B.
is a range gate circuit, 44A and 44B are high-pass filters, 45A and 45B are square circuits, 46 is an adder, 47 is an input line, 48 is an output line, 49 and 50 are multiplexed blocks, and 51 is a delay circuit. are shown respectively. Here, 41A,
41B, 42A, and 42B constitute a quadrature detector.

The range gate circuit 43A is a type of sample and hold circuit, and has a configuration as shown in FIG. Second
In the figure, 52 is an operational amplifier, 53 is a resistor, 54 is a capacitor, and SL and 82 are switches. In FIG. 2, when switch S2 is turned on (closed) while switch S1 is off (open), the output drops to O level, and when switch S2 is turned off (open), switch S1
is turned on (closed) at time t, the range gate circuit 43
A operates as an integrator and switches S1 at time t+Δt.
When the switch S2 is turned off, the output maintains the value at time t+Δt. The range gate circuit 43B has the same configuration as the range gate circuit 43A.

Now, the fixed phase reflected wave from the blood vessel wall is expressed as A(t)si
n (ωt+θ), and the reflected wave including the phase change due to the Doppler effect from blood is B(t-an)sin(ω+bn
). Note that n is the transmission repetition number and b = -ωa.

Here, if the above two waves overlap, then the input signal C
(t) is C(t)=A(t) sin (ωt+θ) +B(t
-an) sin(ω+bn), and simply detecting this signal would result in 1 of B(t-an)=1. It is not possible to sample points. Therefore, multipliers 418 and 41
Multiply C(t) by sin and cos signals by B, D,
Create (t) and (t”).

D/ (t) = C(t) sin ωt = A(t) sin (ω is 10)・sin ωt+B(t
-an) sin(ωt+bn) -sin ωt=A
(t) (-1/2(cos(2ω 10)-cos
θ))+B(t-an) (-1/2(cos(2ω
t+bn) -cosbn) )D, (t)2C(t)
cos ωt = A(t) sin (ωt+θ)・cos ωt+B(t
-an) sin(ωt+bn) ・cos ωt=A
(t) (1/2(sin(2ωt+θ)+sin
θ))B(t-an) (1/2(sin(2ωt+b
n)+5inbn)) where low pass filter 42A, 4
2B removes the ω and 2ω components and passes only the components below that, E・(1)“1/2 A(t) °c・
・#+1/2 B(t-...)...b・
1, E, (t) = 1/2 A(t) ・sin θ
+1/2 B(t-an) sinbn. here,
The range gate circuits 43A and 43B calculate 1=1 for each n. When the sampled time series data is passed through high-pass filters 44A and 44B, E7(t), E,
Each first term of (t) disappears, leaving only the second term with increasing n.

Ft (n)=1/2 B(t-an)cosbnF
, (n)=1/2 B(t -an)sinbn This is squared by the square circuits 45A and 45B, respectively, and the adder 3
6, the sum of squares is obtained as follows: G(n)=1/4 B''(t-an), and a value containing only the desired B (to-an) can be obtained.

As the first amplitude value sample/hold circuit 22 and the second amplitude value sample/hold circuit 23 in FIG. 3, an amplitude value constructed from a quadrature detector consisting of parts 41A, 41B, 42A, and 42B in FIG. 1 and a block 49 is used. Using the value sample hoarding circuit, the sample volume SV1. of FIG. The length of SV2 in the ultrasound beam direction can be substantially increased, and even when blood cell flow as shown in Fig. 4 is present, the two sample volumes SVI and SV can be
2. The number of blood cells that pass through the method can be increased compared to the conventional method.

In the conventional example shown in Fig. 3, an ultrasonic pulse Doppler current meter 31 is used to measure the blood flow velocity in the direction of the ultrasound beam.
1, a correlation detection type ultrasonic blood flow meter can also be used. In this case, a correlation detection type ultrasonic blood flow meter in the beam direction is constructed by the orthogonal detector shown in FIG. 1, blocks 49 and 50, and the cross-correlation peak time difference detection circuit 24 shown in FIG. The signals E+ and E2 may be input to the block 50, and the output of the block 49 and the output of the block 50 may be input to the cross-correlation peak time difference detection circuit 24.

That is, the blood flow velocity in the beam direction can be obtained by correlating signals from two points separated along the beam direction. In the case of a correlation detection type ultrasonic blood flow meter in the beam direction, the time during which the switch S1 of the range gate circuit is on is shortened. Of course, a conventional sample and hold circuit can be used instead.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to obtain a correlation detection type ultrasonic blood flow meter that can always accurately detect blood flow velocity without being affected by the direction of blood cell flow. I can do it.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of the amplitude value sample/hold circuit of the present invention, Fig. 2 is a diagram showing an example of the configuration of a far range gate circuit, and Fig. 3 is a diagram showing a conventional ultrasonic pulse current meter. , FIG. 4 shows the first amplitude value sample/hold circuit 22 and the second amplitude value sample/hold circuit 22 in the ultrasonic pulse current meter shown in FIG.
FIG. 3 is a diagram illustrating a problem when a simple sample-and-hold circuit is used as the hold circuit 23. 11... Control circuit, 12... Ultrasonic drive circuit, 13... Transducer, 14... Switch, 15... Amplifier, 16... 17 is a delay circuit,
18 and 19...Adder, 20 and 21...Reception amplifier, 22...First amplitude value sample/hold circuit, 23
...Second amplitude value sample/hold circuit, 24...
Cross-correlation peak time difference detection circuit, 25... Speed calculation circuit, 31... Ultrasonic pulse Doppler current meter, 32...
・Vector calculation circuit 41A and 41B... Multiplier, 4
2A and 42B...Low pass filter, 43A and 43B...
・Range gate circuit, 44A and 44B...High-pass filter, 45A and 45B...Squaring circuit, 46...Adder, 47...Input line, 48...Output line, 49 and 50
...Multiplexed block, 51...Delay circuit 5
2...Operation amplifier, 53...Resistor, 54...Capacitor, Sl and 82...Switch.

Claims (1)

[Claims] A correlation detection type ultrasonic blood flow meter includes a quadrature detector that detects reflected ultrasound signals using sine wave and cosine wave reference waves, respectively, and quadrature detectors on the sine wave side and cosine wave side of the orthogonal detector. Two range gate circuits each receiving a detection output, a high-pass filter connected to the output side of the two range gate circuits, and a circuit for calculating the sum of squares of the output signals of the two high-pass filters. and a circuit for calculating the cross-correlation of two sum-of-square signals.